The premise of the show is that the cast members infiltrate various settings to figure out who's acting, and who's real. In the clip above, Hyoyeon and Kim Dong Hyun attend a workout class for the girl group trainees, run by a suspicious(?) trainer.
The trainer demonstrated various 'animal training' moves that help create the 'girl group figure'. He first started out with the 'bear move', then followed up with the 'crab move', making both Hyoyeon and Kim Dong Hyun burst into laughter. Check out a clip from this week's broadcast of 'Where is Mr. Kim? 2' above!